Why do I feel this way

So I've had my period for 4 days already and I still think I can be pregnant I haven't told anyone and it's obviously that I'm not but why do I feel like I can be pregnant I've felt so emotional like I always do but I feel it even more this time my period has been brown but that doesn't mean anything bc I had sex a month ago it can't be implantation bleeding and I'm just curious if this has happened to anyone? Ah I'm really concernd like has my obsession of me wanting to be pregnant be so bad that my brain actual thinks I can be pregnant